Section 67(1)(a) in The West Bengal Panchayat Elections Act, 2003
(a)any ballot box or any ballot paper used or intended to be used at a polling station at any time before or after the commencement of poll or during counting is unlawfully taken out of the custody of the Presiding Officer, or is accidentally or intentionally destroyed or is lost, or is damaged or tampered with, to such an extent, that the result of the poll at that polling station cannot be ascertained, or